Apparatus and method for enhancing the uniform etching capability of an ion beam grid

ABSTRACT

A shaper for an ion beam gun has a thin, flat plate with a non-symmetrical profile including notches and tabs. The shaper is mounted to the surface of an ion beam grid having an array of holes. The shaper is oriented radially on the grid and covers some of the holes in the grid. The grid is mounted to an ion beam gun above a specimen that is rotated beneath the ion beam gun. The ion beam is filtered into smaller ion beamlets by the grid. The ion beamlets permeate the holes in the grid that are not covered by the shaper. The ion beamlets reach the specimen to etch it more uniformly than a grid that does not have a shaper. The shaper may be further optimized for a particular grid via a trial-and-error process to even further refine the uniformity of etching depth.

This Divisional Application claims the priority of parent applicationSer. No. 10/252,963, filed on Sep. 13, 2000 now U.S. Pat. No. 6,663,747,and entitled “Apparatus and Method for Enhancing the Uniform EtchingCapability of an Ion Beam Grid”.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to an improved magnetic headslider fabrication process, and in particular to a method and apparatusfor increasing uniformity of the air bearing surface (ABS) of a slider.Still more particularly, the present invention relates to a method andapparatus for improving the capacity of an ion beam grid to uniformlyetch an ABS specimen.

2. Description of the Prior Art

Generally, a data access and storage system consists of one or morestorage devices that store data on magnetic or optical storage media.For example, a magnetic storage device is known as a direct accessstorage device (DASD) or a hard disk drive (HDD) and includes one ormore disks and a disk controller to manage local operations concerningthe disks. Disks are rigid platters, typically made of aluminum alloy ora mixture of glass and ceramic, covered with a magnetic coating.Typically, two or three disks are stacked vertically on a common spindlethat is turned by a disk drive motor at several thousand revolutions perminute (rpm).

The only other moving part within a typical HDD is the head stackassembly. Within most HDDs, one magnetic read/write head or slider isassociated with each side of each platter and flies just above or belowthe platter=s surface. Each read/write head is mounted on a suspensionto form a head gimbal assembly (HGA). The HGA is then attached to asemi-rigid arm apparatus that supports the entire head flying unit.Several semi-rigid arms may be combined to form a single armature unit.

Each read/write head scans the surface of a disk during a Aread@ orAwrite@ operation. The head and arm assembly is moved utilizing anactuator that is often a voice coil motor (VCM). The stator of a VCM ismounted to a base plate or casting on which the spindle is also mounted.The base casting is in turn mounted to a frame via a compliantsuspension. When current is fed to the motor, the VCM develops force ortorque that is substantially proportional to the applied current. Thearm acceleration is therefore substantially proportional to themagnitude of the current. As the read/write head approaches a desiredtrack, a reverse polarity signal is applied to the actuator, causing thesignal to act as a brake, and ideally causing the read/write head tostop directly over the desired track.

In a typical magnetic head slider fabrication process, ion milling hasbeen one of the more popular techniques to form an air bearing surface(ABS) on the slider. The ABS allows the slider to be flown very close toa disk in order to retrieve or rewrite information in the disk. With theincreasing demand on storage density, fly height (i.e., the altitudethat the slider flies at relative to the disk) has become the mostcritical parameter to differentiate drive performance. In order to havesufficient control of the fly height, the etch depth uniformity of theABS must be improved beyond the present tooling capacity.

As graphically illustrated in FIG. 1, the etch depth uniformity of aspecimen 11 is typically controlled by an ion beam etching device 13 viaa grid 15 formed from a durable material such as molybdenum. Specimen 11is rotated as shown on a table 17 about its center, or grid 15 isrotated relative to specimen 11. Grid 15 is mounted to a stationary ionbeam gun 19 directly above specimen 11. Grid 15 has a large number ofsymmetrically spaced-apart holes 21 and voids 22 that are free of holes21 (see FIG. 2). The center 23 of grid 15 is concentric with the centerof specimen 11. As specimen 11 is rotated, ion gun 19 emits a largeaxially-directed beam 25 onto the upper surface of grid 15 such that agrid filters beam 25 and small ion beamlets 27 permeate each of holes 21to etch specimen 11. Although it is possible to redesign the grid usingcomplicated ion optics theories in order to enhance the etch depthuniformity of the ABS, this solution is difficult and relativelyexpensive. Thus, an improved apparatus and method for increasing theuniformity of ABS etching depth is needed.

SUMMARY OF THE INVENTION

A shaper for an ion beam gun is a thin, flat plate having a generallyelongated, non-symmetrical profile with notches and tabs. The shaper ismounted flat to the surface of an ion beam grid having an array ofholes. The shaper is oriented radially on the grid from its center to aperimeter of the grid and covers some of the holes in the grid. The gridis mounted to an ion beam gun above a specimen that is rotated beneaththe ion beam gun. The large ion beam is filtered into smaller ionbeamlets by the grid. The ion beamlets permeate the holes in the gridthat are not covered by the shaper. The ion beamlets reach the specimento etch it more uniformly than a grid that does not have a shaper. Thisphenomena is due to blockage of the higher ion beam density along theradial direction. The ion beamlets that ultimately arrive at thespecimen are themselves more uniform and can produce the more uniformpattern on the specimen. The shaper may be further optimized for aparticular grid via a trial-and-error process to even further refine theuniformity of etching depth.

The foregoing and other objects and advantages of the present inventionwill be apparent to those skilled in the art, in view of the followingdetailed description of the preferred embodiment of the presentinvention, taken in conjunction with the appended claims and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, advantages and objects of theinvention, as well as others which will become apparent, are attainedand can be understood in more detail, more particular description of theinvention briefly summarized above may be had by reference to theembodiment thereof which is illustrated in the appended drawings, whichdrawings form a part of this specification. It is to be noted, however,that the drawings illustrate only a preferred embodiment of theinvention and is therefore not to be considered limiting of its scope asthe invention may admit to other equally effective embodiments.

FIG. 1 is a schematic side view of a prior art ion beam etching devicein operation;

FIG. 2 is a plan view of a prior art ion beam grid used by the device ofFIG. 1;

FIG. 3 is a plan view of a first embodiment of an ion beam grid shaperconstructed in accordance with the invention;

FIG. 4 is a plan view of a second embodiment of an ion beam grid shaperconstructed in accordance with the invention;

FIG. 5 is a plan view of a third embodiment of an ion beam grid shaperconstructed in accordance with the invention and shown mounted to agrid;

FIG. 6 is a plot of etch depth uniformity on a specimen etched with aprior art grid;

FIG. 7 is a plot of etch depth uniformity on a specimen etched with agrid equipped with the shaper of FIG. 3; and

FIG. 8 is a plot of etch depth uniformity on a specimen etched with agrid equipped with the shaper of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 3, a first embodiment of a shaper 31 for an ion beamgun, such as the one illustrated and described in FIG. 1, is shown.Shaper 31 is essentially a thin, flat sheet or plate formed from adurable material such as molybdenum. In the preferred embodiment, shaper31 is formed from the same material as the ion beam grid that the ionbeam grid will be attached to. Shaper 31 is also uniquely shaped for theparticular application of its design and, thus, is precisely customizedvia an empirical or trial-and-error process. Shaper 31 has an elongatedneck portion 33 with a mounting hole 34, a generally rectangular frontportion 35, and a bulkier mid-section 37 that generally tapers to asmall tail portion 39. Mid-section 37 typically has a unique,non-symmetrical profile including notches 41 and tabs 43 that increaseion beam etching uniformity.

A second illustrative embodiment of shaper 31 is depicted in FIG. 4 asshaper 45. Shaper 45 is substantially similar to shaper 31 includingneck, front, middle, and tail portions, but has a slightly differentgeometry as shown.

Although Ashapers@ are widely used in ion beam sputter deposition ordirect ion beam deposition to achieve uniform deposition, those priorart devices differ significantly from the present invention that ismounted directly to the ion beam gun itself. The shaper used indeposition is typically in front of the substrate being deposited. Bymanipulating the shaper position relative to the incoming flux ofdepositing material, the thickness uniformity of the resultant film maybe improved. This type of shaper is used in DC, RF sputtering, as wellas ion beam sputter deposition systems. However, it is not suitable foretching uniformity because the shaper would be etched away and become asource of contamination. The present invention places the shaper insidethe ion gun, such that no such concern exists.

In operation, a third illustrative embodiment of a shaper 51 is shownmounted directly to an ion beam grid 53 having a large plurality ofholes 55 and voids 57 that are free of holes 55. The surface area ofshaper 51 is relatively small compared to the overall surface area ofgrid 53 and typically covers less than 5% of grid, preferably 1 to 5%thereof. Shaper 51 may be secured to either the upper or lower surfaceof grid 53 via a number of different fastening methods including screws.The hole 59 in the neck portion of shaper 51 is aligned and fastened tothe center of grid 53. The remainder of the body of shaper 51 covers aradial swath of grid 53 and extends from the center of grid 53 to aperimeter thereof and is secured with an appropriate number of fasteningmechanisms. In this version, the mid-section and tail portion of shaper51 are used to cover one of the voids 57 in grid 53. With shaper 51rigidly attached to grid 53, a significant number of the holes 55 ingrid 53 (but less than 5%) are covered or sealed. The geometry of shaper51 is determined by the etch depth profile along the radial direction ofgrid 53.

Grid 53 is then mounted to the lower end of a stationary ion beam gun(see FIG. 1) which is located directly over a rotatable table supportingan ABS specimen. Grid 53 may be parallel to the specimen or skewedrelative thereto. As the table rotates the specimen concentricallybeneath the gun, ion beamlets permeate the holes 55 in grid 53 that arenot covered by shaper 51. The ion beamlets that are allowed to reach thespecimen etch a more uniform ABS on the specimen than a grid 53 that isnot configured with a shaper 51. This phenomena is due to the blockageof the higher ion beam density along the radial direction. The ionbeamlets that ultimately arrive at the specimen are themselves moreuniform and, thus, produce an even more uniform pattern on the specimen.Since shaper 51 reduces the ion beam density emanating from grid 53,there is a reduction in the total beam intensity and a concomitantreduction in the etching rate (about 5%) at a given beam power. However,a much better uniformity is achieved. Shaper 51 may be further optimizedfor grid 53 via an empirical or trial-and-error process to even furtherrefine the uniformity of etching depth.

Referring now to FIG. 6, an illustrative plot 61 of the surfaceuniformity of the specimen 11 etched by grid 21 of FIG. 2 is shown. Thevertical axis of FIG. 6 depicts the vertical dimension or depth (inangstroms) of the etching in the surface of specimen 11, and thehorizontal axis depicts the radial distance (in millimeters) from thecenter of specimen 11. In other words, plot 61 is essentially anenhanced cross-sectional view of specimen 11 that schematicallyillustrates the flatness and uniformity of its ABS. The average etchdepth of specimen 11 is 5,215 angstroms with a standard deviation of 214angstroms or 4.1%.

FIG. 7 is a plot 63 of the surface uniformity of a specimen etched by agrid equipped with shaper 31 of FIG. 3. The vertical and horizontal axesof FIG. 7 are the same as for FIG. 6. The average etch depth of thespecimen etched via shaper 31 is 4,918 angstroms with a standarddeviation of 108 angstroms or 2.2%. This is a significant improvementover the previous grid 21 having no shaper. Shaper 31 reduced thestandard deviation by almost half compared to the prior art apparatusand method. Although shaper 31 was a significant improvement, itovercompensated the middle portion of the ion beam by blocking too manybeamlets in this area. Thus, shaper 45 of FIG. 4 was designed to furtherrefine shaper 31.

FIG. 8 is a plot 65 of the surface uniformity of a specimen etched by agrid equipped with shaper 45. The average etch depth of the specimenetched via shaper 45 is 4,966 angstroms with a standard deviation of 85angstroms or 1.7%. This is an even greater improvement over prior artgrid 21 having no shaper, and over a grip equipped with shaper 31.Shaper 45 offers an improvement of about 58% over grid 21, and about 23%over shaper 31. As stated previously, a shaper may be further optimizedfor a particular grid via trial-and-error to even further refine theuniformity of etching depth.

The invention has several advantages. The apparatus and method disclosedabove improves etch depth uniformity with a shaper that can be optimizedwithout redesigning the ion beam grid using complicated ion opticstheories. The shaper of the present invention blocks the higher densitybeam portions to achieve a more uniform ion beam and, thus, a moreuniform etch. The shaper of the present invention improves the etchingdepth uniformity of an ion beam gun by over 50% in some applications.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention.

What is claimed is:
 1. A method of etching a specimen, comprising thesteps of: (a) providing an ion beam gun with a grid having a surfacewith a plurality of holes extending through for filtering a ion beamemitted by the gun; (b) supporting the specimen adjacent to the gun androtating one of the specimen and the gun relative to the other; (c)omitting an ion beam from the gun through the grid and toward thespecimen; and (d) blocking at least some of the holes in the grid bycovering a radial swath of the grid from a center of the grid to aperimeter of the grid such that the ion beam emitted by the gun isprevented from passing therethrough for improving an etch depthuniformity of the specimen.
 2. The method of claim 1 wherein step (d)comprises mounting a plate to the surface of the grid to block said atleast some of the holes.
 3. The method of claim 1 wherein step (d)comprises blocking approximately 1 to 5% of the holes in the grid. 4.The method of claim 1, wherein step (b) comprises rotating the specimenrelative to the gun.